Process for treating antimony drosses



, found in such oxide drosses.

as, ices arm-:1) STATES PATE O C PROCESS FOR TREATING ANTIMONY DROSSES Thomas R. Jones, Woodbrldge, N. 3., assignor to The American Metal Company, Limited, New

York, E, a corporation of New York Application July 3, 1943, Serial No. 493,432

(Cl. 75-113) I 11 Claims.

- magnesium.

The principal'object of the present invention is to provide a simple, efiicient process for the substantial separation of antimony and arsenic, if present, from lead and many other constituents In accordance with my invention, in treating these drosses'by my process, I may obtain a product which is a highly purified antimony oxide substantially free from lead and other impurities. Such antimonyoxide may be used directly, for example,'in the enameling business as an opacifier, or the oxide may be reduced to antimony metal and employed in that form. In producing such highly purified antimony oxide by my procchloride or other ammonium halide and heated in a. retort. Fumes containing the antimony and arsenic together with part of other volatile, me-

tallic components) are collected in a wet gas f scrubber or similar device, while the lead and other metallic components remain in the retort as a residue.

In carrying outfthe process using a substan- I tially pure antimony and lead oxide drosssuch adross is obtainable by' the practice of known processes. I treat such dross in accordance with my invention preferably as shown on the flow sheet designated as Fig. 1, which with Fig. 2 accompanies this specification and forms part thereof. As shown in Fig. 1, the dross is mixed with ammonium chloride employing approximately of the order of 25% excess over the amount theoretically required to react with all lead, antimony and arsenic present. The materials are preferably mixed dry in ground condition. They are then placed in a retort and heated in the range of about'350 C. to below 950 C., preferably to at least about 500 C. (930 F.) for emcient operation. A fume is formed containing arsenic and antimony as chlorides. This fume is collected in a wet gas scrubber which condenses the gases.

ass, I preferably start with an antimony-lead oxide dross from which substantially all other impurities have been removed. Under such cir-' cumstances, it is only necessary to separate the antimony from the lead in order toobtain the highly purified antimony oxide.

0n the other hand, I may employ my process to purify drosses which contain one or more oi;

the other metals mentioned above. For example, but without limitation, I may use the process to remove substantially all of the antimony and The lead remains in the retort as chloride. The antimony trichloride, together with ammonia, are collected in thewater of the scrubber where they react to form insoluble antimony trioxide and soluble ammonium chloride. Any arsenic present as chloride also reacts with the ammonia. to produce arsenic oxide and ammonium chloride. The liquor andsolids thus resulting are filtered. The

solids consisting of antimony oxide, together with some arsenic oxide, are then treated by known recovery processes to recover the antimony as oxide or as antimony metal;

arsenic, if present, from the dross, which dross may then be employed to produce a, solder or other product substantially free from antimony and arsenic.

The invention accordingly consists of a process for separating antimony and arsenic, if present. from an impure dross containing lead and the last-mentionedmaterials, together with othermetallic values, which comprises, combining the dross with an ammonium halide and heating to distill off the antimonycompound formed. together with the arsenic compound if arsenic is present inthe dross. Th'e antimony (and arsenic) are thenrecovered. a

= According to my invention, these ontimonylead oxide materials with or without other me- The. pr'ocessis preferably conducted cyclically and the filtrate from the liquor and solids men-.

tioned above, which contains ammonium chloride and ammonium hydroxide, passes to a leach tank. Into this leach tank the retort residue consistin substantially'of lead a chloride is fed. A reaction occurs whereby lead hydroxide is formed,

together with ammonium chloride. The liquor and solids trom this reaction are filtered. The

solids consistingsubstantlally or lead hydroxide J are then passed to the lead-recovery process for this-liquor is fed back tothe .wet scrubber and" part or it passes to an evaporatorwhere it is,

time components, are treated with ammonium II the production of litharge or metallic lead. The

liquid obtained from the last-mentioned filtering Process contains ammonium chloride. Part of evaporated tcrecover solid ammonium chloride the chlorides of the metals. ,In operating with antimony, lead and arsenic, it is possible to effect alniost a, complete separation of antimony chloride from lead chloride by operating at the temperature mentioned above, namely, about 500 C. This will be apparent from the fact that antimony chloride boils at about 223 (2., whereas lead chloride boils at about 950 C. Arsenic trichloride (AsClz) boils at about 130 C. or 90 degrees lower than antimony chloride and, hence, it distilis over with antimony if present. The reaction as indicated below. produces ammonia (NHs) andwater and when antimony trichloride (SbCla) passes into the wet scrubber, a reaction occurs whereby antimony oxide (SbzOs) is precipitated, as well as ammonium chloride (NHiCl) The arsenic chloride reacts in the same way as antimony and precipitates as arsenic ox- ,ide (Assam) There appear to be several chemilead reaction is caught in the scrubber to form NH4OH so that the liquor is soon ammoniacal because this ammonia is not converted to NH4C1 because the corresponding lead chloride remains in the retort.

The flow sheet shown in Fig. l describes the process as apflied to a dross containing arsenici As indicated, this arsenic may be removed by known processes from the final antimony oxide obtained in order to secure a pure antimony oxide, if that is required. As an alternative, of course, arsenic can be removed from the bullion iromwhich the dross is made, by a process such as that described in the application of Heberlein et al., Serial No. 433,464, filed March 5, 1942, now Patent No. 2,335,758, Nov. 30,.1943. This process will leave the lead and antimony substantially intact. If a dross formed from such metal is used, the antimony oxide resulting from'the practice of my invention will be substantially free from arsenic...

The lead chloride remaining in the retort may I be treated in other ways than as indicated in the cal reactions involved in my process. The reactions involving dissociation of ammonium chloride, formation of antimony trichloridefrom antimony oxide, and the re-formation of the antimony oxide in the scrubber,

as follows:

Above 350 C. (665 F.), NHCl decomposes in accordance with the following equation:

The hydrochloric acid (HCl) then reacts with the antimony oxide thus: I

Combining these two equations, the net reaction becomes:

Sb2Oa+6NH4Cl=2SbCla+6NHs+3320 The three products of the net reaction fume scrubber may be explained by the simple reversal of the net reaction above due to the reduction in temperature to below 350 C. as follows:

by the dissolving of ammonia and antimony trichloride in the water of the gas scrubber with the formation of NH4OH whichreacts with the anti appear to be.

flow sheet of Fig. 1 if desired. For instance, it may be stirred with zinc to'form lead and zinc chloride as marketable products, or may be mixed with crushed limestone and combined with a reducing agent. Upon heating, calcium chloride will be formed and the lead oxide produced will be reduced to metallic lead.

The followingare examples of the manner in which I now prefer to practice the process on dross consisting substantially of lead and antimony oxides, together with a small amountof arsenic and with negligible quantities of other metals'present. In the'examples 1-4 given below, the parts are given by weight.

Example 1 To 150 parts of antimony-lead dross containin; approximately the following content calculated as metals:

Per cent Lead Antimony--- 32.8 Arsenic 2.33

' theoretically required to react with the lead,

The course of the reaction may also be explained mony trichloride to cause antimony oxide to pr It was found during the experiments made in the development of this process that the reaction with lead oxide (PbO) namely,

to chloride with a consumption of NH4C1 correemndinntn .t'hn lead nresent. The NH: from the antimony and arsenic present. After mixing, the mass was placed in a fire clay retort and heated for about 3 /2 hours at about 550 C. The gases were passed into a scrubber, where antimony oxide was precipitated out together with arsenic oxide, lead chloride remaining in the retort. The precipitate in the scrubber upon analysis showed the following:

Lead About 0.1 Antimony oxide About 88.38 Arsenic oxide About 6.71 Balance including moisture 4.81

The. retort residue showed upon analysis to con tain calculated as metals:

The filtrate from the scrubber liquor, after removal of the antimony and arsenic oxides, contained ammonia and about 1% of metallic im- Per cent 0 tion is not to be considered as limited thereto purity. The filtrate was employed tor the treatment oi. the lead chloride in the retort to produce lead oxide and ammonium chloride. The ammonium chloride was then reused as indicated in the flow sheet of Fig. 1.

Example 2 Another antimony-lead dross was employed'in this process containing approximately 44.74% lead,v 41.2% antimony and 0.8% arsenic, calculated as metals, with a small amount of, other metallic values. Approximately'the theoretical proportion or ammonium chloride wasmixed dry with the dross, the other conditions of temperature, etc., being substantially the same as in Example l. The result of the'processemploying the dross mentioned was to produce a scrubber product havingabout the followingcomposition:

- Per cent Lead oxide Trace Antimony oxide ,About 98.14 Arsenic oxide About 1.41

. The retort residue contained substantially all of the leadof the original dross. Fig. 2- shows a flow sheet for antimony dross containing not only lead and arsenic, but also other metals as oxides, specifically, tin, bismuth,

silver, copper and iron. This flow sheet shows where such metals will be found where one or more are present in appreciable quantity. The procedure for operating with such dresses is substantially the same as heretofore given. Part of the tin and bismuth accompany the antimony and arsenic and are recovered therewith, the remaining metals accompany the lead and are except as indicated in the appended claims.

- Example 3 To 150 parts of tin-antimony-lead rim containing approximately the following content I calculatedasmetals:

' Per cent Lead 7 44.20 Tin 37.76 Antimony 2.38 Arsenic recovered therewith The process of my invention is particularly useiul for thepurification of such dresses by removal or antimony and arsenic therefrom substantially completely.

As shown in Fig. ,2, the dross is mixed with dry ammonium chloride and placed in the retort 1 and heated as described in connection with the new sheet of Fig. 1. A fume of antimony, arsenic, tin and bismuth chloride occurs. which is collected in the wet scrubber. The liquor and solids, which latter are composed of the fumed metals as oxides, are filtered and the solids consisting of antimony oxide, arsenic oxide, tin and bismuth oxides are recovered; The antimony content may then be later recovered either as the metal or"as' the antimony oxide by known processes. The filtrate containin ammonium chloride and ammonia then passes to the leach tank into which is then fed the'retort residue consisting of. chlorides, of lead, zinc, silver, cop- P r, iron and the remainder of the tin and bis-, muth. These chlorides are converted by'the ammonia into the corresponding oxides with the production of a Iurther quantity of ammonium chloride. After the reaction, the mixture is filtered and the solids consisting of the oxides of the metals mentioned are recovered. From these solids the lead is recovered by known processes. The filtrate containing ammonium chloride is then passedin part to the wet scrubber and in part to an evaporator; From the latter, solid ammonium chloride the make-up with a further quantity of antimony dross.

The followingexamples, in accordance with the flow sheet of Fig. 2, showthe use of the process as applied to a dross consisting principally of oxides of lead, antimony, tin and arsenic. These examples are illustrative and the invenls recovered for added parts or dry ammonium chloride (NHlCl). The quantity or ammonium chloride added is about 25% in excess of the amount theoretically required to react with the lead, tin,

- antimony and-arsenic present. After mixing,

the mass was placed in a fire-clay retort and heated ror about 3% hours at about 455 C. The gases were passed into a scrubber, where antimony oxide was precipitated out together with arsenic oxide and tin oxidesubstantiallyall oi' the lead and most of the tin remaining as chlorides in the retort. The precipitate in the scrubber upon analysis showed the following calcu- A The filtrate from the scrubber liquor, after removal or the tin, antimony and arsenic oxides, contained substantially no metallic impurity. It was employed for the treatment of the lead chloride in the retort to produce lead oxide, tin

oxide, and ammonium chloride. The ammonium chloride was then reused as indicated in the flow sheet of 2. o 2

Example 4 v, V

To parts of tin-antimony-lead dross con-' taining approximately the following content calculated as metals: 1

- Percent Lead 44.20 Tin 37.76 Antimony 2.38 Arsenic 0.61

and a negligible quantity of other metals, was added 140 parts of dry ammonium chloride (NI-I401). The quantity of ammonium chloride added is about 25% in excess of the amount theoretically required to react with the lead, tin,

antimony and arsenic present. After mixing, the mass was placed in a fire-clay retort and heated for'about 3% hours at about 505 C. "The gases were passed into a scrubber, where antimony oxide was precipitated out together-with arsenic oxide and tin oxide, substantially all offthe lead and most-of the tinremaining. as chlorides in the retort. The precipitate in the scrubber upon analysis showed the following calculated as vmetals;

v 0.61 and a negligible quantity of other metals, was

The above Examples 1-4 employ ammonium 3 ing the dross'with ammonium chloride, heating Per cent Lead Trace fin 49.86 Antimony 11.28

- Arsenic l 2.79 p 5 The retort residue showed on analysis to-contain calculated as metals:

Per cent Lead 41.6 Tin 33.28 Trace Trace The filtrate from the scrubber liquor, after re moval of the tin, antimony and arsenic oxides,

chloride was then reused as indicated in the flow 2o sheet of Fig. 2. In carrying out the processes of Examples 3 and 4, it will he noted that some tin passes to r the scrubber precipitate. A higher proportion of cipitate of Example 4 than in that of Example 3 due to the use of a higher temperature in Ex-- ample 4. Most of the tim operating at preferred may he held back in the retort residue by the addition, if desired, of phosphoric an acid to the retort charge. The phosphorus will then appear with the residue recovered from the retort charge and may be eliminated therefrom chloride as the ammonium halide for operation of the process- Otherhalides than ammonium chloride may be employed if desired. Tests indicate that ammonium fluoride operates similarly to the action of ammonium chloride. Results ob- 40 tained using ammonium bromide are like those H with the use of ammonium chloride. What I claim as new and desire to be secured by Letters Patent is:

1. A process for separating antimony from an impure dross containing antimony and lead which comprises, combining the dross with an 'ammonium halide, heating to distill the antimony halide from the lead halide together with amture below the boiling point of thelead halide, and condensing the fume.

2. A prom for separating antimony from an impure dros containing antimony and lead as its chief constituents which comprises, combining the dross with ammonium chloride, heating to- Iorm antimony chloride, lead chloride, ammonia and water, off the antimony chloride,

and water, as a mixed fume, at a. temperature below the boiling-point of the lead chloride and condensing the fume.

3. A process for separating antimonyfrom an impure dross containing lead. and antimony which comprises, combining the dross with ammonimn chloride, heating a mixture of the dross a5 and ammonium chloride to above about 350 C. but below about 950? C.. causing antimony to distill oi as antimony chloride, together with ammania and water, condensing the gases whereby a. mixture of" antimony oxide and ammonium 7o in a range of about 350 C. to about 600 C. to form antimony chloride, lead chloride, ammonia and water, and distilling off the: antimony chlodross, heating to change the antimony and lead into chlorides and to ca'use the antimony chloride to pass off, together with ammonia and other volatile impurities as fume, passing the fume into a wet scrubber, producing antimony oxide together with ammonium compounds and water' and recovering the antimony oxide from the ammonium compounds solution.

6. A process for treating an antimony dross containing antimony oxide and-lead oxide which comprises, mixing ammonium chloride with said dross, heating to change the antimony and lead -into chlorides and to cause the antimony chloride to pas oii, together with ammonia and other Inn to antimony appears in the scrubber pre- 25 monium chloride with said dross, heating to 5 change the antimony and lead and other oxide compounds into chlorides and to cause the antimony chloride to pass off, together with ammonia and other volatile impurities as fume,

passing the fume into a1 wet scrubber, producing antimony oxide together with ammonium chloride and water, taking the unvolatilized lead chloride and other unvolatilized metallic chloride, combining them with the liquor containing ammonium chloride and ammonia to form lead oxide and other oxide byrcaction of the ammonia with lead chloride and other metallic chloride, thereby increasing the content of ammonlum chloride in the liquor and recovering I the lead oxide and other oxidefrom said liquor. moma. and water as a mixed fume at a. tempera- 5o 8. A process for treating an antimony dross containing antimony oxide, leadoxide and other metal-oxides capable of forming chlorides, which comprises, mixing ammonium chloride with said dross, heating to change the antimony, lead and other metal oxide into chlorides and to cause the antimony chloride. to pass off, together with ammonia and other volatile impurities as fume,

passing the fume into a wet scrubber, producing antimony voxide together with ammonium chloride and water, taking the unvolatilized lead chloride and other unvolatilized metallic chloride, combining them with the liquor containing ammonium chloride and ammonia to form lead oxide and other metallic oxide by reaction of the ammonia. with lead chloride and other metallic chloride, thereby increasing the content of ammonium chloride in the liquor,- evaporating the ammonium chloride solution to recover the ammonium chloride therefrom, and recoverin; the lead oxide and other oxideirom said liquor.

9. A-process for treating anantimony dross containing antimony, lead, arsenic and tin which comprises, mixing ammonium'chloride with said its chief which comprises, comb drosaandheating to change the antimony, lead,

arsenic and tin into chlorides and to cause the antimony and arsenic chlorides to pass on sub stantially completely with ammonia and water asfume and condensing the fume, cleaning the lead chloride substantially undistilled together with some tin chloride.

10. A process fOr treating an antimony dross containing antimony, lead, arsenic and tin which comprises, mixing ammonium chloride with said 'dross, heating to. change the antimony, lead,

arsenic and tininto chlorides and to cause the antimony and arsenic chlorides to pass off-substantially completely as fume together with ammonia and water, and passing the fume into a wet scrubber to condense same to form antimony is and arsenic oxide and ammonium compounds, leaving the lead chloride substantially undistilled together with some tin chloride.

11. A process for treating antimony and lead,

maining solution to the undistilled mass containing lead halide to precipitate the lead.

' Thomas R. JONES. 

